John Edwards, the vice-presidential running mate to Democratic candidate John Kerry in 2004, has launched a new run for the White House in 2008.
Mr Edwards chose the storm-hit New Orleans to launch his campaign
"I'm here to announce I'm a candidate for president of the United States," the 53-year-old former North Carolina senator said in New Orleans.
He said his priorities were to reduce poverty, tackle global warming and cut the number of US troops in Iraq.
Mr Edwards is the third man to launch his bid for the Democratic nomination.
He now joins outgoing Iowa Governor Tom Vilsack and Ohio Representative Dennis Kucinich.
Mr Edwards could potentially compete against his former partner on the Democratic ticket. However Mr Kerry has not said yet whether he will run.
Another two important potential candidates - Senator Barack Obama and Senator Hillary Clinton - are still to announce their plans.
Mr Edwards announced his intention to run for the presidency in a series of television interviews during a visit to New Orleans which was devastated by last year's Hurricane Katrina.
"I've reached my own conclusion this is the best way to serve my country," Mr Edwards told NBC.
"I've learned since the last campaign that it's great to identify a problem... but the way you change things is by taking action."
Outlining his priorities, Mr Edwards said Iraq was one of the biggest issues facing the nation.
"It would be a huge mistake to put a surge of troops into Iraq," he told ABC.
"It sends exactly the wrong signal. We can maximise our chances for success by making clear we are going to leave Iraq and not stay there forever," Mr Edwards added.
He also vowed to restore America's "moral authority and leadership role in the world", end "the shame of poverty", lead "the fight against global warming" and break the US "addiction" to oil.
Staff of Mr Edwards let slip his plans by accidentally launching his campaign website on Wednesday - a day early.
The website carried the logo "Tomorrow begins today" before being shut down.
Mr Edwards' adviser, Jennifer Palmieri, said: "Better a day earlier than a day late."
Mr Edwards has headed a University of North Carolina poverty research centre since the 2004 defeat.